Field of the Invention
The present invention relates to an image forming apparatus which forms an image on a sheet.
Description of the Related Art
In an image forming apparatus, such as a copier and a printer, a sheet with an image formed thereon is discharged to a sheet stacking unit by a discharge roller pair. In an image forming apparatus, a discharge roller pair conveys a sheet with an image formed thereon in an accelerated state, and then releases the sheet toward a sheet stacking unit in a decelerated state (see Japanese Patent Laid-Open No. 2009-57169). The sheet is accelerated once to shorten the printing time. The sheet is released toward the sheet stacking unit in a decelerated state to improve stackability (alignment property) in the sheet stacking unit. The sheet is accelerated once also to elongate a distance from a subsequent sheet to detect the subsequent sheet reliably.
While the discharge roller pair is conveying the preceding sheet at a high speed, the subsequent sheet is conveyed by an image forming unit at an image forming speed (a low speed). If the discharge roller pair and the conveyance roller pair located upstream of the discharge roller pair in the conveyance direction are to be driven by the same motor to reduce the cost, the following problem may occur. Control of the motor to accelerate the discharge roller pair conveying the preceding sheet also accelerates the conveyance roller pair. The accelerated conveyance roller pair cannot receive the subsequent sheet that is fed at a lower speed from the image forming unit.